﻿using System.Collections.Generic;
using System.Linq.Expressions;

namespace PhuDinhCommon
{
    public class ParameterRebinder : ExpressionVisitor
    {

        private readonly Dictionary<ParameterExpression, ParameterExpression> map;



        public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
        {

            this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();

        }



        public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map,
                                                   Expression exp)
        {

            return new ParameterRebinder(map).Visit(exp);

        }



        protected override Expression VisitParameter(ParameterExpression p)
        {

            ParameterExpression replacement;

            if (map.TryGetValue(p, out replacement))
            {

                p = replacement;

            }

            return base.VisitParameter(p);

        }

    }
}